I have an antenna that needs 100 ohm twin lead to match the impedance
of the feed point. The 450 ohm lead has messed up the match and
screwed up the resonance, does anone know of such an animal?
K4WYS

"Sonny Hood" wrote in message
...
I have an antenna that needs 100 ohm twin lead to match the impedance
of the feed point. The 450 ohm lead has messed up the match and
screwed up the resonance, does anone know of such an animal?
K4WYS


Hi Sonny

Would you consider using two lengths of 50 ohm coax, side by side?

Jerry

Sonny Hood wrote:

I have an antenna that needs 100 ohm twin lead to match the impedance
of the feed point. The 450 ohm lead has messed up the match and
screwed up the resonance, does anone know of such an animal?
K4WYS

Sonny, the feedline cannot and does not have any influence on the
resonance of an antenna. Resonance is determined by the physical
dimensions of the antenna itself.

Tell us about the antenna. How did you determine a 100 ohm input impedance?

72 ohm twin lead is available at selected suppliers. But, I am not aware
of anyone making 100 ohm twin lead. that's why I asked about the 100 ohm
value.

Dave wrote:
Sonny, the feedline cannot and does not have any influence on the
resonance of an antenna. Resonance is determined by the physical
dimensions of the antenna itself.

Feedline length has every influence on the resonance of
an antenna system if the SWR is not 1:1.

Why is a G5RV resonant on 3.7 MHz when a 102 foot dipole
is resonant on 4.6 MHz?

Truth is that the feedline can be used to resonate the
antenna system. I resonate my 130 ft. dipole on any HF
band by varying the length of the feedline. Check it out
at: http://www.qsl.net/w5dxp/notuner.htm
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:

Dave wrote:

Sonny, the feedline cannot and does not have any influence on the
resonance of an antenna. Resonance is determined by the physical
dimensions of the antenna itself.


Feedline length has every influence on the resonance of
an antenna system if the SWR is not 1:1.


C'mon Cecil, you know better!

The antenna is resonant 100% by itself.

100 feet of wire is resonant within a few KHz of 4.68 MHz. Period.
120 feet of wire is resonant at ~ 3.9 MHz. Period.
65 feet of wire is resonant at ~ 7.2 MHz. Period.
33 feet of wire is resonant at ~ 14.2 MHz. Period.

You are tuning a non resonant antenna to resonance with your stubs.

You changed the scope of the discussion with the exact wording of your
response. You used "antenna system". I used "antenna".

Why do you persist in comparing alligators and kittens?

Dave wrote:
The antenna is resonant 100% by itself.

Most knowledgeable people know that the resonant frequency
of the antenna system can be changed by the length of the
transmission line series matching section. Why don't you
know that? Here is the SWR of my 130 foot dipole antenna
on 40m achieved by varying the length of the 450 ohm
transmission line.

http://www.qsl.net/w5dxp/swr13040.gif

Please look at that graph and then tell us that the feedline
cannot tune the antenna system to resonance.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote in news:x0N9g.86749$dW3.29542
@newssvr21.news.prodigy.com:

Dave wrote:
Sonny, the feedline cannot and does not have any influence on the
resonance of an antenna. Resonance is determined by the physical
dimensions of the antenna itself.

Feedline length has every influence on the resonance of
an antenna system if the SWR is not 1:1.

Why is a G5RV resonant on 3.7 MHz when a 102 foot dipole
is resonant on 4.6 MHz?

Truth is that the feedline can be used to resonate the
antenna system. I resonate my 130 ft. dipole on any HF
band by varying the length of the feedline. Check it out
at: http://www.qsl.net/w5dxp/notuner.htm

All true, but there isn't much difference between a G5RV and a 102 foot
dipole fed with 450 ohm line to a good balanced tuner.

Back years ago I had a very effective vee dipole antenna for 80m that was
composed of two identical wires from the top of my third story shack
window insulated and tied off to trees and shrubbery. I fed it with
home-made 600 ohm line, about six feet long and tapped it directly off
the tank coil of my amplifier. It was LOUD all over the Pacific, South
America, audible in Africa, but for some reason, nothing from Europe!

--
Dave Oldridge+
ICQ 1800667

Dave Oldridge wrote:
... there isn't much difference between a G5RV and a 102 foot
dipole fed with 450 ohm line to a good balanced tuner.

Not much difference in performance. Lots of difference in the
impedances seen by the tuner. For instance, built-in autotuners
will usually match a G5RV somewhere on 80m, 40m, & 20m. There
are usually certain troublesome lengths of 450 ohm line used with
a 102 foot dipole that will prohibit a match by built-in autotuners.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote in news:dY%9g.76844$H71.68934
@newssvr13.news.prodigy.com:

Dave Oldridge wrote:
... there isn't much difference between a G5RV and a 102 foot
dipole fed with 450 ohm line to a good balanced tuner.

Not much difference in performance. Lots of difference in the
impedances seen by the tuner. For instance, built-in autotuners
will usually match a G5RV somewhere on 80m, 40m, & 20m. There
are usually certain troublesome lengths of 450 ohm line used with
a 102 foot dipole that will prohibit a match by built-in autotuners.

True, I'm somewhat spoiled since I've always used fairly wide-range tuners.
Even my Intellituner will match a 64-1 load.

--
Dave Oldridge+
ICQ 1800667

Sonny Hood wrote:

I have an antenna that needs 100 ohm twin lead to match the impedance
of the feed point. The 450 ohm lead has messed up the match and
screwed up the resonance, does anone know of such an animal?
K4WYS

Use side-by-side runs of 50 ohm coax to achieve a balanced Z0
of 100 ohms. Tie the braids together at both ends.
--
73, Cecil http://www.qsl.net/w5dxp